Mirrored VR Window doesn't want to Maximize neither go fullscreen

Hello,

Firstly,thank you for what your shared!

I try to copy this code into 4.12 gamemode.cpp ,and Include #include “Engine.h” to solve the errors about “GEngine”.Then I override gamemode on WorldSetting, nothing happen .Do i miss some steps?

I also use HTC vive to test.

Thans for your reply!